Traditionally, gold recovery or refining from Dore gold or from gold alloy scrap, such as jewelry, has required the services of highly specialized and trained refiners because of the complexities of the processes involved and the dangers inherent in the use of materials involved in such complex processes. Previous to the late 1970s, gold in a pure state was extracted from ores or solutions by alkaline sulphides, leaching, or certain cyanide compounds which are extremely poisonous and dangerous.
During the late 1970s, when the price of gold dramatically increased, methods utilizing aqua regia or alkaline cyanide solutions became popular for this purpose. As stated previously, these prior art processes are very dangerous to human personnel because of the poisonous chemicals involved. The processes are also complicated and slow.
In a recent U.S. Pat. No. 4,182,671, issued Jan. 8, 1980, an electrolytic silver and gold refining cell and process is disclosed employing as an electrolyte a solution of apparently concentrated nitric acid and silver nitrate (a poisonous substance) in order to form silver at the cell cathode and gold at the anode.
One object of the present invention is to improve on the known prior art in general pertaining to gold recovery or refining and, in particular, to improve on the prior art exemplified by U.S. Pat. No. 4,182,671. This improvement involves, among other things, simplification of the process and the apparatus for carrying out the process. The process is rendered much safer, faster, more economical and more versatile in the present invention and the process and apparatus embodying the invention are utilized solely for refining gold and not for the refining of other metals. Concerning the apparatus, a number of components required in the prior art have been entirely eliminated. As a result of such simplifications, there is no longer a need to employ highly specialized and highly trained technicians for monitoring the process and apparatus and great skill is not required for these purposes. It is thought that the most important aspect of the invention is the use of a mild nitric acid solution in the electrolytic cell to refine gold to 99.9% purity where the gold alloy forming the slab anode is free of platinum or other platinum metals.
Other objects and advantages of the invention will become apparent to those skilled in the art during the course of the following description.